Issues when battery powered

[coldib]

Hello! I want to build my own weather station that periodically transmits temperature every hour using MQTT via WiFi. Everything works fine when powering the ESP32 via USB or via 5V using a YW Robot Power MB V2 - however, when I try to power it using 4xAA with a DC Buck Modul AMS1117 or a 3,3V input using YW Robot Power MB V2 it seems to get stuck in a boot loop. I guess this is due to the spikes created when using WiFi - when turning off WiFi for testing reasons the ESP32 seems to run stable.

Any suggestions how to get this to work?

[ESP_Sprite]

Your text does not make sense - for one, the LM1117 is not a buck module. Can you draw a schematic of what you have, and also list the *specific* components you're using?

[coldib]

Sure!

I use the following components:

[*] AMS1117: http://www.advanced-monolithic.com/pdf/ds1117.pdf
[*] AZDelivery ESP32-WROOM-32 with CP2102: https://cdn.shopify.com/s/files/1/1509/ ... 1598356497
[*] 4 x NiMH AA-Battery 2000 mAh
[*] DHT22

Schematics:

IMG_1718.jpg (44.37 KiB) Viewed 8764 times

[ESP_Sprite]

Okay, clear, all separate modules. What may be happening here is that the impedance between battery, AMS1117 and ESP32 is too high because you e.g. use jumper wires. Could you try connecting the batteries directly to the 'V5' input on that devboard? The devboard already has a built-in LDO and that way you make use of that: it's more likely to have proper decoupling as well.

[coldib]

Hello! Sorry for the late replay but this did not help unfortunately. Do you have any other suggestions? Regards

[Chevelle]

OK. I get where you are going but what you are showing in your schematic is not the way to get there.

First off, 4 AA batteries at 1.2V each gives a total of 5.8 volts. That gives your 5V regulator only 0.8V to work with. I see that it is an LDO but that still isn't much margin and it will go away as the voltage drops from use. Consider using 6 or 8 batteries or even a 9V.

Also, that regulator is an adjustable regulator. I needs a resistor network to set the proper output voltage. Finally, that regulator is way more than you need. Even in full transmit mode, the ESP32 doesn't need anywhere near that ouput current and your sensor needs just a few mils at amost. Look for an fixed LDO in the 250-500 mA range.

If you use the proper regulator and a battery pack with some more room in it, you will be far better off. Get the regulator circuit running before you connect anything else to it.

Now if you really want to do it right, ditch the development kit and use the ESP32 module directly and select a 3.3V compatable sensor. (There must be plenty.) Now the whole thing will easily run on your 4 AA pack.

I'm happy to help which ever way you go.